This ranking of the tracks is a result of combining a series of numerical data measured for every single stop with certain qualitative variables that are impossible to convert into numbers. For example, using brakes in the Mexican GP, where the temperature of the tarmac reaches 122°F, is totally different from their use in the British GP where the air temperature doesn't go over 68°F.
At the Autodromo Hermanos Rodriguez, ventilation is crucial to prevent overheating the calipers and discs, which in any case operate well in temperatures of up to almost 1832°F. To avoid this problem, each team uses a personalized cooling system obtained through 1,400 ventilation holes in each disc.
In Silvestone, on the other hand, the single-seaters risk excessive cooling and the consequent grazing of the friction material. The carbon that the discs and pads are made of does not guarantee generating the right friction at operating temperatures that are too low, which can jeopardize the braking performance.
The number of braking sections required to complete a lap is a misleading variable for assessing the stress a system undergoes. In Montreal, the drivers use their brakes seven times per lap and in Monte Carlo they use them twelve times, in addition to the track being 0.62 miles shorter than the Canadian track. Still, the circuit on Notre Dame Island is ranked Very Hard on the brakes while the Monaco track is just Medium.